A clamp is a device used to join, grip, support, or compress mechanical or structural parts. Clamps use opposing, often adjustable sides or parts for bracing objects or holding them together.
One type of clamp is an adjustable bar clamp. Adjustable bar clamps typically are made of three main components: a drive unit integral with a jaw, a bar that is advanced by the drive unit, and an opposing jaw that is connected to the bar. A workpiece is positioned between the clamps when the clamps are used to compress the workpiece. The clamps may also be positioned to function as a spreader. These clamps are typically hand-actuated and are known to exist in many varieties.